A GNOME desktop session occurs between the time that a user logs in to the GNOME desktop and the time that the user logs out. The session manager starts after the Login Manager authenticates the user. The session manager enables the user to manage the session. For example, a user can save the state of a session and return to that session the next time that the user logs in.
At a minimum, the following applications run in a session:
The session manager, gnome-session.
The GConf X settings daemon, gnome-settings-daemon.
The gnome-panel application, which runs the panels on the GNOME desktop.
The Metacity window manager.